DGIST Scholar: High-performance quantum dot light-emitting diodes using crosslinked hole transport materials based on dibenzo[b,d]furan

Department of Energy Science and Engineering Theses Master

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High-performance quantum dot light-emitting diodes using crosslinked hole transport materials based on dibenzo[b,d]furan

Title: High-performance quantum dot light-emitting diodes using crosslinked hole transport materials based on dibenzo[b,d]furan

Author(s): Jaehyoung Park

DGIST Authors: Jaehyoung Park ; Youngu Lee ; Seungho Choe

Advisor: 이윤구

Co-Advisor(s): Seungho Choe

Issued Date: 2023

Awarded Date: 2023-08-01

Type: Thesis

Description: Solution-processed(용액 공정); High-performance QLEDs(고효율 양자점 발광 다이오드); Cross-linkable hole transport material(열 가교성 전공 수송 물질); Blend(혼합); Small molecule(단분자)

Table Of Contents: Ⅰ. Introduction 1
Ⅱ. Theorical Background 5
2.1 Qunatum dot light-emitting diodes (QLEDs) 5
2.1.1 Quantum Dots (QDs) 5
2.1.2 Core Structure of QDs 5
2.1.3 Surface Passivation of QDs 6
2.2 Device Structure of QLEDs 7
2.2.1 All-Organic Materials Device Structure 7
2.2.2 Hybrid Materials Device Structure 8
2.2.3 All-Inorganic Materials Device Structure 8
2.3 QLEDs Device Mechanisms 8
2.3.1 Molecular Orbitals of Electrons 8
2.3.2 Charge Transfer and Recombination Mechanisms 10
2.4 Progress in Device Configuration 12
2.4.1 Top-Emitting QLEDs 12
2.4.2 Inverted QLEDs with All-Solution Processing 13
2.4.3 Tandem QLEDs 14
2.5 Fabrication of QLEDs devices 15
2.5.1 Vacuum process 15
2.5.1.1 Physical vapor deposition 15
2.5.1.2 Chemical Vapor Deposition 17
2.5.2 Solution process 18
2.5.2.1 spin coating 18
2.5.2.2 inkjet printing 19
2.6 Strategies for Enhancing QLEDs Devices 20
2.6.1 Enhancing QD Structure 20
2.6.2 Optimizing Device Architecture 21
2.6.2.1 Attaining Charge Equilibrium via a Hole Transport Materials 21
2.6.2.2 Attaining Charge Equilibrium via an Electron-Blocking Layer 23
2.6.2.3 Establishing Charge Equilibrium through a Hole-Spacing Layer 23
2.7 The uses of hole transport materials for solution process 24
2.7.1 Solvent resistance 24
2.7.2 Enhancing the properties of hole transport materials 24
2.7.2.1 Double hole transport layers 25
2.7.2.2 Blending hole transport materials 25
Ⅲ. Experimental methods 26
3.1 Materials and Characterization 26
3.2 Device fabrication 26
3.2.1 Fabrication of green QLEDs 26
3.2.2 Fabrication of hole only device 27
Ⅳ. Results and discussion 28
4.1 Blend crosslinked HTMs 28
4.2 Cross-linking test 29
4.3 Optical properties 30
4.4 UPS Analysis 33
4.5 Charge balance analysis 36
4.6 TRPL Analysis 37
4.7 AFM Analysis 38
4.8 Contact angle 40
4.9 QLEDs device performance 41
4.10 Lifetime measurement 46
Ⅴ. Conclusion 47
REFERENCES 48
SUMMARY 51